My Book Duo RAID 1 constant drive usage

hi,
It’s been a month since i got the drive so i am assuming that spotlight has indexed every file on that drive. Yet the drive never stops. It’s driving me crazy. I simply unplug it when i’m not working on my photos. Any idea what could be the issue? Time machine is enabled. The comp has been turned on for a week and BookDuo is still spinning (reading/writing) despite no software running.

Thanks for any input,
Jurand